1. Field of the Invention
The present invention relates to an accessory for a power hand tool and more particularly, to a screw nail magazine for an electric screwdriver.
2. Description of the Related Art
A conventional screw nail magazine A, as shown in FIGS. 1 and 2, comprises a fixed holder member A1, a movable holder member A2, a spring member A3, a positioning member A4, a belt track A5, a belt drive member A6, and a nailing depth adjustment device A7. The fixed holder member A1 is adapted to be affixed to the housing of an electric screwdriver. The movable holder member A2 is mounted in the fixed holder member A1 and movable backwards and forwards on the fixed holder member A1 in a predetermined path. The spring member A3 is set between the fixed holder member A1 and the movable holder member A2. The positioning member A4 is mounted on the movable holder member A2, having a contact portion A41 for stopping against the work surface where a screw nail is to be driven in or turned out. The belt track A5 is mounted on the movable holder member A2 to support a belt B that carries a row of screw nails and to provide a moving path for the belt B. The belt drive member A6 is mounted on the movable holder member A2 and adapted to move the belt B in the path provided by the belt track A5. The nailing depth adjustment device A7 is mounted on the fixed holder member A1 and adapted to control the nailing depth of the electric nailing tool. When in use, the belt B is mounted on the belt track A5 and extending over the belt drive member A6, and then the fixed holder member A1 of the screw nail magazine A is fastened to the electric screwdriver, keeping the driving blade of the electric screwdriver located inside the movable holder member A2 at a position relative to the inner side of the belt B. During working, the pressed portion A41 of the positioning member A4 is pressed on the work surface with one screw nail of the belt B aimed at the selection location at the work surface, and then a force is applied to the electric screwdriver against the work surface. At this time, the movable holder member A2 and the positioning member A4 are moved into the inside of the fixed holder member A1, enabling the driving blade of the electric screwdriver to stop at the respective screw nail against the work surface. When starting the electric screwdriver at this time, the respective screw nail is driven into the work surface.
The nailing depth adjustment device A7 limits the depth of the retraction of the movable holder member A2 in the fixed holder member A1, thereby effectively controlling the nailing depth of the electric screwdriver. The nailing depth adjustment device A7 comprises a stop block A71 and a lock screw A72. The stop block A71 is provided in the fixed holder member A1, having a beveled stop face A711. The lock screw A72 has a head A721 and a threaded shank A722. The threaded shank A722 is inserted through an elongated slot A11 on the fixed holder member A1 and connected to the stop block A71 in the fixed holder member A1. When fastened up the lock screw A72 after having moved the lock screw A72 along the elongated slot A11 to the selected position, the stop block A71 is locked to the fixed holder member A1 at the desired location. When the positioning member A4 is moved with the movable holder member A2 backwards to the inside of the fixed holder member A1, the beveled stop face A711 of the stop block A71 stops a complementary beveled face A42 at the positioning member A4, thereby limiting the nailing depth. When loosened the lock screw A72, the lock screw A72 can be moved along the elongated slot All to change the position of the stop block A71 in the fixed holder member A1, thereby adjusting the nailing depth of the electric screwdriver.
However, when loosening the lock screw A72, the lock screw A72 may be disconnected from the stop block A71. In this case, the user must remove the screw nail magazine A from the electric screwdriver and then detach the parts of the screw nail magazine A so that the lock screw A72 can be fastened to the stop block A71 again. After the lock screw A72 and the stop block A71 have been connected together, the user must install the movable holder member A2, the belt track A5 and the spring member A3 in the fixed holder member A1 in proper order again. This procedure is complicated, wasting much time. Further, it is also complicated to adjust the position of the stop block A71, increasing the user's work time.